Typical carbon membrane synthesis methods known in the prior art involve mechanical rolling of thermally expanded graphite flakes, chemical vapor deposition, as well as vacuum filtration of graphene sheets or carbon nanotubes solution. In these methods used to date, it is difficult to realize large-scale production of CMs with well-defined pore architectures and controlled morphologies. These are long-felt problems in the field that are unresolved.
When used in electron microscopy, carbon membranes have been known to be produced as either a continuous film, such as in graphene layers or amorphous carbon films, or perforated in patterned or random geometries to leave open spaces in the membrane. The membranes, ranging in thickness from a single atomic layer (graphene) up to 250 nm or more, are typically supported on a grid-form made from Cu or Ni with apertures. However, carbon is a relatively inert substrate, so sample preparation often involves glow-discharge cleaning to improve wettability. Carbon membranes also have no active surface to create an affinity for a particular material.
Carbon materials have also been widely researched in their use in addressing global energy and environmental issues due to their tunable physicochemical properties, rich abundance, and low cost. Morphology control of carbon materials at atomic/nano/micro-sized scales is highly important from the view of practical applications, but these problems with morphology control are long-felt, unresolved issues. For instance, various shapes and morphologies of carbons, such as carbon quantum dot fibers, nanospheres, vesicles, and membranes have been proposed to be developed, and among these morphologies are macroscopic freestanding porous carbon membranes (CMs), but theses shapes and morphologies continue to encounter precision and control problems.
Existing methods known in the prior art have not supported precise control over morphology, pore architecture, or bottom-up production approaches, which has continued to hinder the advanced applications of freestanding carbon membranes (CMs), particularly in the fields of nanotechnology and carbon nanoelectronics. Continuing problems exist in the prior art regarding achievement of hierarchical pore architectures possessing interconnected pores over different length scales from micro- to meso- and to macropores, which have hindered the ability to offer rapid mass/energy transport through large pores and simultaneously high reaction capacity through the large active surface area provided by nanopores. In spite of tremendous efforts in recent years to synthesize hierarchically structured porous carbon membranes, all these difficulties have persisted to plague the technological field without a solution, including the failure to solve the problems associated with structural complexity, multistep templating reactions or post-processing of carbon membranes.